engleski

Gastrointestinal stability of oleuropein from wild olive leaf extract after simulated digestion process using human digestive enzymes

The olive tree is well-known as the excellent source of phenolic compounds exhibiting a vast spectrum of biological activities. Olive leaves are the richest source of olive phenolic compounds, particularly oleuropein, which has many beneficial effects on human health. This study compares the gastrointestinal stability of pure oleuropein and oleuropein from olive leaf extract (OLE), after a two-phase simulated digestion process (gastric and duodenal) with human digestive enzymes. In vitro models that mimic human physiology are recognized as simple, inexpensive and reproducible tools to study the digestive stability of natural compounds. However, in vitro models based on the use of human gastrointestinal enzymes are still very rare. Enzymatic activity of collected human digestive juices was measured spectrophotometrically. The volume of digestive juices corresponding to 1 U of enzymatic activity was 20 uL of human gastric juice and 25 uL for human duodenal juice. The phenolic profile of OLE was determined by UPLC- DAD technique. Oleuropein was dominant in the OLE (85.82%). The presence of other phenolic compounds in the extract was low: hydroxytyrosol (3.63%), luteolin-7-O-glucoside (2.08%), verbascoside (1.11%), tyrosol, catechin, p-coumaric acid, and kaempferol (< 1%). The concentration of oleuropein in un- digested and digested OLE was identified by the UPLC-DAD method. The gastrointestinal stability of pure oleuropein was very high after gastric digestive phase (84.12%) and in acidic medium without digestive enzymes, pH 2.5 (95.25%). Oleuropein digestive stability was significantly lower after duodenal phase (36.64%). Acidic media and gastric digestive enzymes influenced the increase of the concentration of oleuropein in the olive leaf extract (26-35%). In addition, the duration of intestinal phase (120 min) and the slightly alkaline medium (pH=7.5) resulted in the higher concentration of oleuropein in the extract (the concentration increased for 60%). As conclude, oleuropein was quite resistant to gastric digestion but was largely degraded in the intestinal phase.

polyphenols; oleuropein; olive leaf; gastrointestinal stability; human digestive enzymes

Potpora SuRi br. 13.11.1.2.02.